The present invention is directed to a method for the production of decorative laminates which are employed in conjunction with a substrate such as particle board for use in countertops, furniture and the like.
Decorative laminate products may be produced by both low and high pressure lamination processes. In low pressure lamination processes, the pressure employed is less than about 500 psi while high pressure lamination processes employ processes of at least 500 psi.
Various methods can be employed to provide decorative laminates by low pressure lamination. For example, a single opening, quick cycle press can be used where a saturated decor sheet is laminated to a sheet of plywood or particle board. A "continuous laminator" can be used where one or more layers of treated (resin saturated) paper are pressed into a unitary structure as the layers move through continuous laminating equipment between plates, rollers or belts. Alternatively, a laminated sheet (continuous web or cut to size) may be pressed onto a particle board, etc. and a "glue line" used to bond the laminated sheet to the board. Single or multiple opening presses may also be employed which contain several laminates (similar to high pressure presses) but at a pressure below 500 psi.
In making decorative laminates via high pressure lamination, a plurality of sheets are impregnated with a thermosetting resin and stacked in superimposed relation with a decorative sheet placed on top. This assembly is then heat and pressure consolidated at a pressure of at least 500 psi. Generally, more than one laminate is formed at one time by inserting a plurality of sheet assemblies in a stack with each assembly being separated by a release medium which allows the individual laminates to be separated after heat and pressure consolidation.
The laminates so formed are then bonded to a substrate such as plywood, hardboard, asbestos board, particle board, and the like by the use of adhesives such as contact adhesives, urea-formaldehyde, white glues (polyvinyl acetate emulsions), hot melts, phenolic or resorcinol formaldehyde, epoxy, coal tar, animal glues and the like.
It has been found to be desirable during the production of such laminates by either low or high pressure lamination processes to impart abrasion-resistant characteristics to the decorative surface portion of the laminate to enhance the utility of such laminates as table and countertops, wall panels and floor surfacing.
Such abrasion resistance has in the past been imparted to decorative laminates having a printed decorative sheet by means of an applied overlay sheet which provided a transparent barrier over the decorative print sheet. Resin coatings have also been applied to the surface of the laminate which coatings contain abrasion-resistant mineral particles. Note in this regard U.S. Pat. Nos. 3,135,643; 3,373,070; 3,373,071; 3,798,111; 3,928,706; 4,255,480; 4,263,081; 4,305,987; 4,322,468; 4,327,141; 4,395,452; 4,400,423; and 4,430,375.
The above-noted methods, while generally satisfactory results, are undesirable in that they require either the use of additional materials (i.e., the overlay sheet) or the use of additional coating steps. Such disadvantages result in lessened efficiency and cost-effectiveness of the abrasion-resistant characteristics thereby provided.